Slider with integrated thermally-assisted recording (TAR) head and long laser diode with optical body for directing laser radiation

ABSTRACT

A thermally-assisted recording (TAR) slider has an integrated TAR head and an integrated long laser diode, like an external-cavity VCSEL. The TAR head is integrated with the slider at the trailing end and includes an optical waveguide having a grating coupler oriented in a plane generally parallel to the slider trailing end, and a near-field transducer (NFT) at the slider air-bearing surface (ABS) and coupled to the waveguide. A carrier is attached to the slider front end and supports the external-cavity VCSEL so that the linear path of its output laser beam is directed from the slider front end to the slider trailing end. An optical body is attached to the slider trailing end and has an input surface for receipt of the laser radiation from the laser diode, an output surface for directing the laser radiation to the grating coupler, and at least one reflective surface for turning the laser radiation from the input surface to the output surface.

TECHNICAL FIELD

This invention relates generally to a thermally-assisted recording (TAR)disk drive, in which data are written while the magnetic recording layeron the disk is at an elevated temperature, and more specifically to aTAR slider with an integrated TAR head and integrated long laser diode,like an external-cavity vertical-cavity surface-emitting laser (VCSEL).

BACKGROUND OF THE INVENTION

Thermally-assisted recording (TAR), also called heat-assisted magneticrecording (HAMR), has been proposed. In a TAR disk drive, an opticalwaveguide with a near-field transducer (NFT) directs radiation from alaser to heat localized regions of the magnetic recording layer on thedisk. The radiation heats the magnetic material locally to near or aboveits Curie temperature to lower the coercivity enough for writing tooccur by the magnetic field from the write head. The recorded data isread back by a conventional magnetoresistive read head. The TAR head,which includes the optical waveguide, write head and read head, isformed on the trailing surface of a head carrier, such as a slider withan air-bearing surface (ABS) that allows the slider to ride on a thinfilm of air above the surface of the rotating disk. The top surface ofthe slider (the surface opposite the ABS) is attached to aflexure/suspension assembly so that the slider can be moved across thedisk surface by the disk drive actuator. Electrical connections are madefrom the write head and read head to the disk drive electronics byconductors on the flexure/suspension that connect to electrical contactpads on the trailing surface of the slider.

It is desirable to integrate the laser, which is typically a laserdiode, with the slider so that the laser light is directed to theoptical waveguide on the slider. This does not present a significantproblem for laser diodes, like a vertical-cavity surface-emitting laser(VCSEL), which typically have a relatively short length of about 100 μm,as compared to the slider length of about 850 μm. TAR sliders withvarious means for attachment of relatively short laser diodes have beenproposed. For example, in U.S. 20080002298 A1, the laser diode is formedon a substrate surface that faces the trailing end of the slider, andthe substrate is attached by bonding pads that connect the samesubstrate surface directly to the trailing end of the slider. However, atypical VCSEL has power output of about 10 mW, which is not adequate forcurrently proposed TAR disk drives, which need a power output of about50 mW.

Thus more powerful laser diodes, which will typically be longer thanVCSELs, are required for TAR. One type of more powerful and longer laserdiode is an external-cavity VCSEL, where a third mirror is on the backside of the VCSEL semiconductor substrate. The external cavity and thirdmirror allow for higher single mode power than can be achieved with aconventional VCSEL. An external-cavity VCSEL is described in U.S. Pat.No. 6,778,582 B1 and by J. G. McInerney, et al., “High brightness 980 nmpump lasers based on the Novalux Extended Cavity Surface-Emitting Laser(NECSEL) concept”, Proc. of SPIE Vol. 4947 (2003), pp. 240-251. However,because an external-cavity VCSEL has a length of at least at 300 μm andthe length of current disk drive sliders is only around 850 μm, thereare problems in integrating the laser with the slider with the necessarymechanical support, electrical connections and heat sink requirements.In particular, the trailing end of the slider is not a desirablelocation because of limited surface area for attachment and because heatfrom the laser may adversely affect the write and read heads. Also, thetop surface of the slider is not a desirable location because thethickness of the slider (the slider “height” between the ABS and the topsurface) and its connection to the flexure/suspension assembly cannot beincreased without increasing the disk-to-disk spacing in the disk drive,which would undesirably increase the overall size of the disk drive.

What is needed is a TAR slider with an integrated laser diode longerthan 300 μm, like an external-cavity VCSEL, that is not attached to theslider top or trailing surfaces.

SUMMARY OF THE INVENTION

The invention relates to a TAR slider with integrated TAR head and anintegrated relatively long (greater than 300 μm) laser diode. The laserdiode may be an external-cavity VCSEL. The external-cavity VCSELincludes a semiconductor substrate with the VCSEL formed on one surface,an external cavity on the opposite surface, and an output third mirroron the output surface of the external cavity. The external-cavity may bethe semiconductor substrate or the semiconductor substrate together witha block of material that is transparent to the laser radiation and isattached to the semiconductor substrate. The TAR head is integrated withthe slider at the trailing end and includes an optical waveguide havinga grating coupler oriented in a plane generally parallel to the slidertrailing end, and a near-field transducer (NFT) at the slider ABS andcoupled to the waveguide. A carrier is attached to the slider front endand supports the external-cavity VCSEL so that the linear path of itsoutput laser beam is directed from the slider front end to the slidertrailing end. An optical body formed of material, like glass or plastic,that is transparent to the laser radiation is attached to the slidertrailing end. The optical body has an input surface for receipt of thelaser radiation from the laser diode, an output surface for directingthe laser radiation to the grating coupler, and at least one reflectivesurface for turning the laser radiation from the input surface to theoutput surface. The grating coupler receives the laser radiation andturns it into the waveguide, which directs the laser radiation to theNFT at the ABS. The height of the carrier, the attached external-cavityVCSEL and the optical body is preferably less than the height of theslider, i.e., the spacing distance between the slider ABS and the slidertop surface opposite the ABS.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the following detaileddescription taken together with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is sectional view of a prior art external-cavity vertical cavitysurface emitting laser (VCSEL).

FIG. 2 is a sectional view through a portion of a disk and anair-bearing slider that supports a thermally-assisted recording (TAR)head according to the prior art.

FIG. 3 is a top view of a slider with integrated TAR head and integratedexternal-cavity VCSEL according to one embodiment of the inventionwherein the carrier is attached to the front end of the slider and anoptical body is attached to the trailing end of the slider.

FIG. 4 is a sectional view along a plane through the length of theslider showing the attachment of the optical body to the slider trailingend and the alignment of the laser radiation beam orthogonal to theslider trailing end for the embodiment of FIG. 3.

FIG. 5 is a view of the grating coupler and waveguide portion accordingto the invention as viewed from a direction orthogonal to the slidertrailing end.

FIG. 6A is a top view of a slider with integrated TAR head andintegrated external-cavity VCSEL according to another embodiment of theinvention wherein the optical body attached to the slider trailing endhas only a single reflective surface.

FIG. 6B is an end view of the slider and attached optical body for theembodiment of FIG. 6A and illustrates the grating coupler and opticalbody attachment being near a side of the slider.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a sectional view of a monolithic external-cavity VCSELaccording to the prior art and as described in U.S. Pat. No. 6,778,582B1 and in the previously-cited article by J. G. McInerney, et al. Theexternal-cavity VCSEL has a semiconductor substrate 10 with frontsurface 10 a, back surface 10 b and thickness L. A VCSEL with activeregion 1 is formed on front surface 10 a and includes gain layer 16located between partially reflecting intermediate Bragg reflector ormirror 14 and bottom Bragg mirror 18, and an oxide layer 22 that definesan aperture 22 a. A partially reflecting output mirror 28 is formed onthe back surface 10 b of semiconductor substrate 10 and functions as athird mirror. The laser radiation is emitted through the third mirror28. The semiconductor substrate 10 with thickness L functions as anexternal cavity for the VCSEL. The external cavity allows for highersingle mode power than can be achieved with a typical VCSEL without theexternal cavity and third mirror. When the external cavity is made fromGaAs, the external-cavity VCSEL may be designed to generate laserradiation with a wavelength of greater than approximately 920 nm. Forexample, the wavelength may be between 920 nm and 1000 nm. Shorterwavelengths require the use of a different substrate due to opticallosses in the in GaAs. The external-cavity VCSEL shown in FIG. 1 is asingle device that has been cut from a semiconductor wafer onto whichthe materials making up the various layers have been deposited andpatterned using well-known semiconductor lithographic and fabricationprocesses. Thus a large number of devices are formed on a single wafer.The materials, dimensions and fabrication methods for theexternal-cavity VCSEL shown in FIG. 1 are described in detail in U.S.Pat. No. 6,778,582 B1.

FIG. 2 is a sectional view through a portion of a TAR disk 100 andair-bearing slider 110 that functions as the head carrier withintegrated TAR head, as proposed in the prior art. FIG. 2 is not drawnto scale because of the difficulty in showing the very small features.The TAR disk 100 is depicted as a patterned-media disk with a disksubstrate 118 and discrete magnetic islands 130 and nonmagnetic regions132. The islands 130 are spaced apart by nonmagnetic regions 132, whichmay formed of polymeric material for planarizing disk 100. The islands130 are magnetized perpendicularly, resulting in the recorded bits beingstored in the recording layer of the islands 130 in a generallyperpendicular or out-of-plane orientation. The islands 130 are discretemagnetic islands that function as the patterned bits. A heat sink layer121 may be located below the islands 130 and nonmagnetic regions 132.The TAR disk 100 may also be a conventional continuous-media magneticrecording disk wherein the recording layer is not patterned but is acontinuous layer.

Also shown on slider 110 with disk-facing surface or air-bearing surface(ABS) is the read head 60 and the write head 50 (with the yoke thatconnects write pole 52 and a return pole 54). The ABS of slider 110 isthe surface that faces the disk 100 and is shown without the thinprotective overcoat typically present in an actual slider. The ABS shallmean the surface of the head carrier that is covered with a thinprotective overcoat, the actual outer surface of the head carrier ifthere is no overcoat, or the outer surface of the overcoat. Writecurrent passes through a coil 56 of the write head 50 to generate amagnetic field (arrow 42) at the write pole 52. This magnetic fieldmagnetizes the recording layer on the island 130 beneath the write pole52 as the disk 100 moves past the write head 50 in the direction ofarrow 123. The detection or reading of the recorded bits is by a readhead 60 having a sensing edge 60 a at the ABS. The read head istypically a magnetoresistive (MR) read head, such as a tunneling MR(TMR) read head in which a sense current passes perpendicularly throughthe layers making up the head. A pair of magnetic permeable shields S1and S2 are located on opposite sides of read head 60 to prevent magneticflux from bits other than the bit being read from reaching the read head60. The write coil 56 is shown as a conventional flat or “pancake” coilwrapped around the yoke that connects the write pole 52 with the returnpole 54, with the electrical current directions being shown as into thepaper by the coil cross-sections marked with an “X” and out of the paperby the coil cross-sections marked with a solid circle. However, the coilmay also be a conventional helical coil wrapped around the portion ofthe yoke that directly supports the write pole 52. The slider 110 withintegrated TAR head has an outer surface or trailing end 115 withelectrically conductive pads (not shown) that connect through theinsulating layers 113 to the read head 60 and coil 56 of write head 50.

The slider 110 also supports a laser 70, mirror 71, optical channel orwaveguide 72 and near-field transducer (NFT) 74, which has its output atthe ABS. The laser 70 and mirror 71 are shown as being supported on thetop surface 150 of slider 110. The spacing between the generallyparallel ABS and top surface 150 defines the height H of the slider 110,which for conventional sliders is in the range of about 180 to 300 μm.The optical waveguide 72 is depicted in FIG. 2 as extending through theyoke of write head 50 and being located between the write pole 52 andreturn pole 54. However the optical waveguide 72 may be located at otherlocations, such as between shield S2 and return pole 54, or between thewrite pole 52 and the outer face of the slider 110. The waveguide 72 isformed of a core material such as Ta₂O₅ or another high index dielectricmaterial that is transmissive to radiation at the wavelength of thelaser and is surrounded by a dielectric cladding layer 73 (for exampleSiO₂ or Al₂O₃) of lower refractive index than the core material. Whilethe slider 110 in FIG. 2 is depicted as supporting mirror 71 fordirecting the laser radiation from laser 70 into waveguide 72, it isknown to use a grating coupler coupled to the waveguide, as describedfor example in U.S. 20090310459 A1.

The NFT 74 is located at the output of waveguide 72 at the ABS of theslider 110. The laser radiation strikes the NFT 74, creatingconcentrated near-field radiation to the islands 130 as the disk rotatesin the direction 123 past the slider 110. A “near-field” transducer, asused herein, refers to “near-field optics”, wherein the passage of lightis to, from, through, or near an element with subwavelength features andthe light is coupled to a second element located a subwavelengthdistance from the first. NFTs typically use a low-loss metal (e.g., Au,Ag, Al or Cu) shaped in such a way to concentrate surface charge motionat a surface feature shaped as a primary apex or tip. Oscillating tipcharge creates an intense near-field pattern. Sometimes, the metalstructure can create resonant charge motion, called surface plasmons orlocal plasmons, to further increase intensity. The electromagnetic fieldof the oscillating tip charge then gives rise to optical output in thenear field, which is directed to the data islands on the disk. The NFT74 has features less than the wavelength of the laser radiation and thespacing between the NFT 74 and the islands is less than the wavelengthof the laser radiation.

When write-current is directed through coil 56, the write pole 52directs magnetic flux to the data islands 130. The dashed line 117 witharrows shows the flux return path back to the return pole 54. The NFT 74directs near-field radiation, as represented by wavy arrow 82, to thedata islands 130 as the TAR disk 100 moves in the direction 123 relativeto the slider 110. The electric charge oscillations in the NFT 74 heatthe data islands 130. This raises the temperature of the magneticrecording material in a data island to near or above its Curietemperature to thereby lower the coercivity of the material and enablethe magnetization of the data island to be switched by the write fieldfrom the write pole 52.

The TAR head elements, i.e., read head 60, shields S1, S2, return pole54, write pole 52, coil 56 and waveguide 72, are fabricated on atrailing surface 112 of slider 110 using well-known conventional thinfilm deposition and patterning techniques. The TAR head is thusintegrated with the slider 110, with resulting trailing end 115.Insulating material, typically alumina, is deposited at various timesduring the fabrication process to separate the various TAR head elementsand refill recessed areas, as shown by insulating layers 113. Theinsulating material generally surrounds the TAR head elements andprovides a portion of the ABS. The slider 110 is typically formed of analumina/titanium-carbide (Al₂O₃/TiC) composite material. The trailingsurface 112 is the surface of a wafer onto which a large number of TARheads are patterned. The wafer is then diced into individual sliderswith the length of the sliders (in the direction perpendicular totrailing surface 112) corresponding generally to the thickness of thewafer. US 20090258186 A1, assigned to the same assignee as thisapplication, describes a wafer-level process for fabricating TAR headswith thin film waveguides and NFTs.

The invention is a slider with integrated TAR head and an integratedrelatively long (greater than 300 μm) laser diode. Preferably the laserdiode is an external-cavity VCSEL. An embodiment of the invention isshown in the top view of FIG. 3. The slider 210 with integrated TAR headhas a top surface 250, a front end 225, a trailing end 215, andgenerally parallel sides 260, 265. The slider has a typical lengthbetween front end 225 and trailing end 215 of about 850 to 1250 μm. TheTAR head is depicted as being integrated with the slider 210 and formedbetween trailing surface 212 and trailing end 215. The TAR head includesa grating coupler 77, which is located in a plane generally parallel totrailing end 215 and is thus depicted in edge view. The external-cavityVCSEL 300 is attached to carrier 400 which is attached to the front end225 of slider 210. The external-cavity VCSEL 300 is mounted to carrier400 so that it is located along a side 265 of slider 210 with its laserradiation beam 350 in the direction from the slider front end 225 towardthe slider trailing end 215. A solid optical body 500 ofradiation-transparent material is attached to the slider 210 and directsthe laser radiation from the external-cavity VCSEL 300 to the gratingcoupler 77.

The external-cavity VCSEL 300 includes semiconductor substrate 310having generally parallel first and second surfaces 310 a, 310 b. Thesemiconductor substrate 310 may be formed of GaAs or AlGaAs. The firstsurface 310 a has deposited on it in succession first Bragg mirror 314,gain layer 316, dielectric layer 322 with aperture 322 a, and secondBragg mirror 318. An annular isolation trench 323 separates secondmirror 318 from the semiconductor substrate 310. A first electrode layer324 a provides electrical contact with second mirror 318 and a secondelectrode layer 324 b provides electrical contact with semiconductorsubstrate 310. The electrodes 324 a, 324 b allow electrical current toflow through the aperture 322 a. The second surface 310 b ofsemiconductor substrate 310 has a block of material 330 attached. Thematerial 330 may be glass or another material transparent to the laserradiation, such as plastic, and may be attached to surface 310 b by aconventional adhesive, such as epoxy glue. The third mirror 328 for theexternal-cavity VCSEL 300 is formed on the output side of material 330opposite to the side attached to semiconductor substrate surface 310 b.As shown in FIG. 3, the semiconductor substrate 310 has a thicknessT_(S) and the block of material 330 has a length L₀. In the embodimentof FIG. 3, the semiconductor substrate 310 and the block of attachedmaterial 330 together function as the external cavity with a lengthL₁=T_(S)+L₀. However, the semiconductor substrate 310 may have athickness of L₀ so that the semiconductor substrate 310 alone functionsas the external cavity, in the manner as shown in FIG. 1. Thesemiconductor substrate 310 alone or together with material 330 may havea total length L₁ in the range of about 300 to 1500 μm.

The carrier 400 is attached to the front end 225 of slider 210,preferably by a layer of adhesive 401 like epoxy, and supports the laserdiode. The carrier 400 is attached at the first surface 310 a of thesemiconductor substrate 310. The carrier 400 may be formed of variousmaterials, including silicon, aluminum nitride ceramic, or berylliumoxide, and fabricated by known microfabrication processes or byconventional machining. The carrier 400 has electrically conductivecontact pads 405 a, 405 b that connect with contact pads 325 a, 325 bconnected to electrodes 324 a, 324 b, respectively, of theexternal-cavity VCSEL 300, preferably by reflow solder joints 406, 408.The electrically conductive contact pads 405 a, 405 b are connected torespective electrically conductive contact pads 407, 409 on the topsurface 402 of carrier 400. The top surface 250 of the slider 210 isattached to a flexure/suspension assembly (not shown) which haselectrical leads that connect to the contact pads 407, 409 and thusallow for electrical connection with the laser diode power supply. Theattachment of the external-cavity VCSEL 300 to carrier 400 by solderreflow joints 406, 408 provides for heat sinking from theexternal-cavity VCSEL 300 through the contact pads 405 a, 405b to thecarrier 400 and back to the front end 225 of slider 210. This preventsheating of the write head and read head, which are located at thetrailing end 225 of slider 210.

An optical body 500 formed of solid material, like any glass or plasticmaterial that is transparent to the laser radiation, is attached toslider 210 and directs the laser radiation from output mirror 328 to thegrating coupler 77. The body 500 is depicted with its input surfaceinput surface 510 being generally parallel to output mirror 328 and thusorthogonal to the laser radiation beam 350. However, the body inputsurface 510 may make an angle with the laser beam 350 to preventrefection back into the external-cavity VCSEL 300. In the embodimentshown in FIG. 3, the body 500 is attached to the trailing end 215 ofslider 210, preferably by a layer of adhesive 501 like epoxy, and has anoutput surface 520 generally parallel to the trailing end 215 of slider210 and two reflective surfaces 512 and 514. Each reflective surface512, 514 may be a collimator mirror of reflective material, like gold oraluminum, patterned on the outer surface of body 500. Reflective surface512 turns the radiation from a direction generally parallel to a side265 of slider 210 to a direction generally parallel to the trailing end215, and reflective surface 514 turns the radiation from a directiongenerally parallel to the trailing end 215 to a direction generallyorthogonal to the trailing end 215. The laser radiation is then directedto output surface 520 and then to grating coupler 77.

FIG. 4 is a sectional view along a plane through the length of slider210 showing the attachment of body 500 by a layer of adhesive 501 to theslider trailing end 215 and the alignment of the laser radiation beamorthogonal to the slider trailing end 215. Dashed lines 210 a, 210 brepresent extensions of the slider planes corresponding to the slidertop surface 250 and bottom surface (ABS), respectively. The carrier 400(FIG. 3), the attached external-cavity VCSEL 300 (FIG. 3), and the body500 are all located preferably within the region bounded by the twoplanes 210 a, 210 b. However, the attached external-cavity VCSEL 300 andthe body 500 may extend slightly above line 210 a if allowed by thedesign of the suspension that attaches to the top surface 250 of slider210, for example by providing a hole in the suspension to allow for theslight extension. Thus the carrier 400, attached external-cavity VCSEL300, and optical body 500 do not substantially increase the overallheight H of the slider, so there is no need to increase the disk-to-diskspacing of the disk drive.

In FIG. 4, the laser radiation beam 350 output from output surface 520has a generally linear path that is depicted as being substantiallyorthogonal to slider trailing end 215. However, the laser beam 350 doesnot have to be orthogonal to slider trailing end 215, but can make asmall angle, which may make the design of coupler 77 easier, asdescribed by Van Laere et al., “Compact Focusing Grating CouplersBetween Optical Fibers and Silicon-on-Insulator Photonic WireWaveguides”, Optical Fiber Communication and the National Fiber OpticEngineers Conference on 25-29 March 2007. The laser beam 350 travelsthrough insulating layer 113 to grating coupler 77 that lies in a planegenerally parallel to trailing end 215. The insulating material 113,typically alumina, is transparent to the laser radiation, which may havea wavelength between about 920 and 1000 nm. The grating coupler 77 turnsthe incoming laser radiation and directs it into waveguide 72, which islocated between cladding layers 73. The waveguide 72 directs the laserradiation to NFT 74 at the ABS. FIG. 5 is a view of grating coupler 77and shows the tapered input end 72 a of waveguide 72 as viewed from adirection orthogonal to trailing end 215. The grating coupler 77 iscoupled to the tapered end 72 a of waveguide 72, which is locatedbetween cladding layers 73. Grating couplers are well-known and havebeen proposed for use in TAR heads, as described for example in U.S.20090310459 A1. Focusing grating couplers and grating couplers coupledto tapered waveguides are described by Van Laere, et al., “CompactFocusing Grating Couplers for Silicon-on-Insulator Integrated Circuits”,IEEE PHOTONICS TECHNOLOGY LETTERS, VOL.19, NO. 23, Dec. 1, 2007, pp.1919-1921.

FIG. 6A is a top view of a slider with integrated TAR head andintegrated external-cavity VCSEL according to another embodiment of theinvention wherein the optical body 600 has input and output surfaces610, 620, respectively, but only a single reflective surface 612. Theexternal-cavity VCSEL 300 is identical to that shown and described inFIG. 3, so not all details are illustrated. The reflective surface 612is located in a plane that makes an angle with the incoming laserradiation beam 350 from output mirror 328 so that it is directed from adirection generally parallel to the side 265 of slider 210 to outputsurface 620 and then through insulating layer 113 to grating coupler 77.The radiation beam 350 is depicted as being generally orthogonal toinput surface 610, but input surface 610 may be oriented to benon-orthogonal to radiation beam 350 to prevent refection back to theexternal cavity VCSEL. The radiation beam 350 enters trailing end 215 ata non-orthogonal angle. The grating coupler 77 is offset from themidline between slider edges 260, 265, but the waveguide 72 (shown indotted lines) to which it is coupled is angled downward toward themidline to NFT 74, which is located at the midline at the slider ABS.FIG. 6B is an end view of the slider 210 and attached optical body 600and illustrates the advantage that the grating coupler 77 and theattachment of optical body 600 are located near a side 265 of the slider210 away from the write head 50 and read head. FIG. 6B also illustratesthat, like the embodiment of FIG. 3, the carrier 400, attachedexternal-cavity VCSEL 300, and optical body 600 do not increase theoverall height H of the slider, so there is no need to increase thedisk-to-disk spacing of the disk drive.

While the present invention has been particularly shown and describedwith reference to the preferred embodiments, it will be understood bythose skilled in the art that various changes in form and detail may bemade without departing from the spirit and scope of the invention.Accordingly, the disclosed invention is to be considered merely asillustrative and limited in scope only as specified in the appendedclaims.

1. A thermally-assisted recording (TAR) head structure for a magneticrecording disk drive comprising: a slider having a disk-facing surface,a top surface opposite to and generally parallel to said disk-facingsurface, a front end, a trailing end and two sides, the slider having aheight defined generally by the distance between the disk-facing surfaceand the top surface and a length defined generally by the distancebetween the front and trailing ends; a laser diode comprising asemiconductor substrate having first and second generally parallelsurfaces defining a length greater than 300 μm, the laser radiation beambeing output from said second surface in a linear path orthogonal tosaid second surface, and contact pads on said first surface; a carrierconnected to the contact pads on said first surface of the semiconductorsubstrate and attached to the front end of the slider, the carrier andconnected laser diode being located substantially within a regionbounded by upper and lower surfaces generally parallel with the slidertop and disk-facing surfaces, respectively, the laser diode beingconnected to the slider's front end and extending along a side of theslider with the laser's linear radiation beam path being in a directionfrom the slider front end to the slider trailing end; and a body ofmaterial transparent to the laser radiation and attached to the trailingend of the slider, the body having an input surface for receipt of laserradiation output from the laser diode, an output surface near the slidertrailing end, and at least one reflective surface for reflecting thelaser radiation from the input surface to the output surface.
 2. Thehead structure of claim 1 further comprising at least two solder jointsconnecting the contact pads of the laser diode to the carrier.
 3. Thehead structure of claim 1 wherein the carrier has a top surfacegenerally parallel to the slider top surface and further comprisingelectrical conductor pads on the top surface of the carrier andconnected to the contact pads of the laser diode.
 4. The head structureof claim 1 further comprising an adhesive connecting the carrier to thefront end of the slider.
 5. The head structure of claim 1 furthercomprising an adhesive connecting the body to the trailing end of theslider.
 6. The head structure of claim 1 wherein said at least onereflective surface on said body comprises a collimator mirror.
 7. Thehead structure of claim 1 wherein the input surface of the body isgenerally orthogonal to the linear radiation beam path output from thelaser diode.
 8. The head structure of claim 7 wherein said at least onereflective surface turns the radiation beam from generally parallel to aside of the slider to generally parallel to the trailing end of theslider, and further comprising a second reflective surface on the bodyfor turning the radiation beam from generally parallel to the trailingend of the slider to generally orthogonal to the trailing end of theslider.
 9. The head structure of claim 1 wherein the body has one andonly one reflective surface and wherein the laser radiation from theoutput surface of the body is non-orthogonal to the slider trailing end.10. The head structure of claim 1 further comprising an opticalwaveguide on the slider oriented generally parallel to the trailing endof the slider, the waveguide having a grating coupler, and wherein theradiation beam from the output surface of the body is aligned with thegrating coupler.
 11. The head structure of claim 10 further comprising anear-field transducer (NFT) coupled to the waveguide and located at thedisk-facing surface.
 12. The head structure of claim 1 wherein the laserdiode is an external-cavity vertical cavity surface emitting laser(VCSEL) comprising a VCSEL on said first surface of the semiconductorsubstrate and having first and second mirrors, a gain layer between themirrors and a dielectric layer having an aperture therein; and an outputthird mirror on the second surface of the semiconductor substrate. 13.The head structure of claim 12 wherein the semiconductor substrate isthe external cavity for the external-cavity VCSEL.
 14. The headstructure of claim 12 further comprising an external cavity between thesecond surface of the semiconductor substrate and the output thirdmirror.
 15. The head structure of claim 12 wherein the external cavitycomprises a layer of material transparent to the radiation from theexternal-cavity VCSEL.
 16. The head structure of claim 1 furthercomprising a write head on the slider and having a write pole at thedisk-facing surface, and a magnetoresistive read head on the slider. 17.A thermally-assisted perpendicular magnetic recording disk drivecomprising: a perpendicular magnetic recording disk comprising a disksubstrate and a perpendicular magnetic recording layer on the disksubstrate; and the head structure of claim 1; wherein the slider ismaintained near the disk with the spacing between the disk-facingsurface and the recording layer being less than the wavelength of thelaser radiation from the laser diode.
 18. The disk drive of claim 17wherein the perpendicular magnetic recording layer is patterned intodiscrete data islands.
 19. A thermally-assisted recording (TAR) headstructure for a magnetic recording disk drive comprising: a sliderhaving an air-bearing surface (ABS) for facing the disk, a top surfaceopposite to and generally parallel to the ABS, a front end, a trailingend and two sides, the slider having a height defined generally by thedistance between the ABS and the top surface; an optical waveguide atthe slider trailing end and having a grating coupler oriented in a planegenerally parallel to the slider trailing end; a near-field transducer(NFT) at the ABS and coupled to the waveguide; an external-cavityvertical cavity surface emitting laser (VCSEL) comprising asemiconductor substrate having first and second generally parallelsurfaces; a VCSEL on a first surface of the semiconductor substrate andhaving first and second mirrors, a gain layer between the mirrors and adielectric layer having an aperture therein; an output third mirroropposite the semiconductor first surface; and an external cavity betweenthe VCSEL and the output mirror; a first electrode connected to thesecond mirror; and a second electrode connected to the semiconductorsubstrate; the external-cavity VCSEL having a generally linear laserradiation beam path from the VCSEL through the semiconductor substrateand the output third mirror; a carrier attached to the front end of theslider and connecting the external-cavity VCSEL to the slider, thecarrier and connected external-cavity VCSEL being located substantiallywithin a region bounded by upper and lower surfaces generally parallelwith the slider ABS and top surface, respectively, the external-cavityVCSEL being connected to the slider with the radiation beam beingparallel to a side of the slider in a direction from the front end tothe trailing end of the slider; and a body of material transparent tothe laser radiation and attached to the trailing end of the slider, thebody having an input surface generally orthogonal to the radiation beamfrom the external-cavity VCSEL's third mirror for receipt of the laserradiation from the third mirror, an output surface near the slidertrailing end for directing the laser radiation to the grating coupler,and at least one reflective surface for reflecting the laser radiationfrom the input surface to the output surface.
 20. The head structure ofclaim 19 wherein the semiconductor substrate is the external cavity forthe external-cavity VCSEL and the output mirror is attached to thesecond surface of the semiconductor substrate.
 21. The head structure ofclaim 19 further comprising material transparent to the laser radiationfrom the VCSEL and located between the second surface of thesemiconductor substrate and the output mirror, wherein the externalcavity comprises the semiconductor substrate and said transparentmaterial.
 22. The head structure of claim 19 further comprising at leasttwo solder joints connecting the first and second electrodes of theexternal-cavity VCSEL to the carrier.
 23. The head structure of claim 19wherein the carrier has a top surface generally parallel to the slidertop surface and further comprising electrical conductor pads on the topsurface of the carrier and connected to the first and second electrodesof the external-cavity VCSEL.
 24. The head structure of claim 19 furthercomprising an adhesive connecting the carrier to the front end of theslider.
 25. The head structure of claim 19 further comprising anadhesive connecting the body output surface to the trailing end of theslider.
 26. The head structure of claim 19 wherein said at least onereflective surface turns the radiation beam from generally parallel to aside of the slider to generally parallel to the trailing end of theslider, and further comprising a second reflective surface on the bodyfor turning the radiation beam from generally parallel to the trailingend of the slider to generally orthogonal to the body output surface.